Lalas was born in Birmingham, Michigan, United States, to a Greek father, Demetrius Lalas and an American mother, Anne Harding Woodworth. His father was a professor who later became the director of Greece's national observatory, while his mother is a writer and poet. Lalas speaks Spanish and Italian, in addition to his native English and Greek.[6]

Lalas attended Cranbrook Kingswood School in Bloomfield Hills, Michigan. Even though he did not begin playing soccer until he was eleven, he had developed his skills enough to be named the 1987 Michigan High School Player of the Year by his senior year. In addition to playing soccer, he was a member and captain of his high school hockey team, which won the state championship. Lalas was rated for the Ontario Hockey League Midget draft in 1987, but was not selected.[7]

Lalas left Rutgers in 1991 to focus on the U.S. national team despite being interested in finishing his degree. He resumed his education in 2013, when Rutgers began offering enough online classes to fulfill what Lalas required to graduate. Lalas took 12 classes and 36 credits over 10 months to finish what he jokingly called "a 26-year plan", earning a bachelor's degree in English with a minor in music in May 2014.[10]

After college and the 1992 Summer Olympics, Lalas trained with former Arsenal player Bob McNab in California. This led to a trial with Arsenal during the winter of 1992. It was quickly determined that Lalas did not have the quality for a first team spot. As a result, Lalas only had a few training sessions with the Reserve team before being cut shortly after his arrival in North London.[11] Lalas then returned home in Detroit and spent a month reluctant about his future in soccer before coach Bora Milutinovic invited him for the United States tryouts in Mission Viejo, California.[12]

Following the 1994 FIFA World Cup, Lalas signed with Italian Serie A club Padova. While Lalas anchored the team's defense and scored three goals off set pieces (including against A.C. Milan & Internazionale), Padova finished the 1994–1995 season at the bottom of the standings. Only after winning a relegation play off on June 10, 1995, did the team ensure its survival in the top ranks for the next season. On June 25, 1995, Major League Soccer (MLS) signed Lalas to play for one of the new league's teams. While MLS had intended to begin playing in 1995, it had run into difficulties and so delayed the first season until 1996. In order to allow Lalas to maintain his match fitness, MLS loaned him back to Padova for the 1995–1996 season. Lalas last played for Padova in a home game against Lazio on February 25, 1996.

Prior to the inaugural Major League Soccer (MLS) draft in February 1996, the league allocated high-profile players throughout the league's ten teams (except for the Dallas Burn, which alone amongst all MLS sides never received a U.S. national team allocation from the 1994 World Cup era). As part of this process, MLS placed Lalas with the New England Revolution. Lalas was a regular on the Revs backline during the 1996 and 1997 seasons. In November 1997, the Revolution loaned Lalas to Ecuadorian First Division Club Emelec for a month. He returned to New England at the end of December only to find himself traded to the MetroStars on February 4, 1998. He spent the 1998 season with the MetroStars before being traded, along with Tony Meola, to the Kansas City Wizards for Mark Chung and Mike Ammann on January 28, 1999. Lalas spent one season with the Wizards before announcing his retirement on October 10, 1999.

Just over a year later, he returned to playing when he signed with the Los Angeles Galaxy as a discovery player on January 14, 2001. Nearly three years later, he retired again, this time permanently, on January 12, 2004.[13]

Lalas earned 96 caps, scoring nine goals, with the U.S. National Team between 1991 and 1998. His first cap came in a 2-2 tie with Mexico on March 12, 1991 in the 1991 NAFC Championship.[14] He gained his second cap four days later in a 2-0 win over Canada. While he started both games, he did not gain another cap until he came on for Fernando Clavijo in a 2-2 tie with Denmark on January 30, 1993. His next game, a start, came on March 23, 1993 in a 2-2 tie with El Salvador. While he became a fixture on the team through the rest of 1993, he did not cement his position as a starter in the U.S. central defense until the beginning of 1994. He went on to start and play all ninety minutes in the four U.S. games of the 1994 FIFA World Cup and was named an honorable mention All-Star. On June 11, 1995, Lalas flew directly from a relegation playoff game with his club team, Padova, in order to appear in the second half of a 1995 U.S. Cup victory over Nigeria.[15] His contributions to the national team led to his selection as the 1995 U.S. Soccer Athlete of the Year. While Lalas was on the roster for the U.S. at the 1998 FIFA World Cup, he never entered a game.[16] His last cap had come in the final U.S. tuneup for the finals, a May 30, 1998 scoreless tie with Scotland where he was a second-half substitute for Earnie Stewart.

Lalas was selected as one of three over age players on the U.S. Olympic teams at both the 1992 and 1996 Summer Olympics.

Lalas has a noted affinity for rock music. He played in a band called The Gypsies ever since college, which even opened European concerts for Hootie & The Blowfish in 1998.[22] The Gypsies were featured in self-produced, self-distributed album Woodland, released by Lalas during the 1994 World Cup,[12] and Lalas has also released three solo albums: Ginger (1998), Far from Close (2008) and Infinity Spaces (2014).[23]